This invention relates to magnetic disk drives, or apparatus for data transfer with magnetic disks such as those commonly referred to as floppy disks, which may be housed in protective envelopes to make up disk cartridges or cassettes. More specifically, the invention pertains to such apparatus featuring means for holding the magnetic disk exactly level as it makes data transfer contact with a transducer head or heads.
In data transfer apparatus of the kind herein under consideration, a magnetic disk is placed on a motor driven turntable in positive engagement therewith, and a pair of transducer heads make data transfer contact with the opposite faces of the disk. The turntable is much smaller in diameter than the magnetic disk to allow the transducer heads to engage the opposite faces of the disk and to travel in its radial direction for track to track accessing. If the magnetic disk is of relatively large size, its flexibility will allow the transducer heads to make proper data transfer contact with the disk in the face of a slight difference in vertical position between the disk bearing surface of the turntable and the disk contacting surface of the lower transducer head.
The current trend, however, is toward the miniaturization of magnetic disks. Take, for example, the flexible magnetic disk cassette recently developed by Sony Corp., of Tokyo, Japan, and disclosed in Japanese Laid Open Patent Application No. 57-36473, laid open to public inspection on Feb. 27, 1982, and in corresponding U.S. Pat. No. 4,445,155 issued Apr. 24, 1984. It has a diameter of only 86 millimeters. The pair of transducer heads will not make proper data transfer contact with such a small sized magnetic disk unless it lies level on the turntable. The leveling of the magnetic disk has heretofore been possible only by manufacturing the disk drive mechanism, head support and transport mechanisms, and other associated parts of the apparatus to very close dimensional tolerances and by assembling them in exact relative positions so that the disk bearing surface of the turntable may be on a level with the disk contacting surface of the lower transducer head. This conventional solution is of course unsatisfactory from the standpoints of cost reduction and higher production constantly sought after by the industry.